The majority of all laminate floors are produced according to a production method generally referred to as Direct Pressed Laminated (DPL). Such laminated floors comprise a core of a 6-12 mm fibre board, a 0.2 mm thick upper decorative surface layer of laminate and a 0.1-0.2 mm thick lower balancing layer of laminate, plastic, paper or like material.
The surface layer of a laminate floor is characterized in that the decorative and wear properties are generally obtained with two separate layers of paper, one above the other. The decorative layer is generally a printed paper and the wear layer is a transparent overlay paper, which comprises small aluminium oxide particles.
The printed decorative paper and the overlay are impregnated with melamine formaldehyde resins and laminated to a HDF core in large discontinues or continuous laminate presses where the resin cures under high heat and pressure and the papers are laminated to the core material. An embossed press plate or steal belt forms the surface structure. Sometimes a structured paper is used as a press matrix.
Laminated floors may also be produced with printing technology. One advantage is that the pressing operation may be avoided and that no printed papers are needed to provide a decorative wear resistance surface.
Floor panels with a Direct Printed Laminate surface comprise the same type of HDF core as DPL. The décor is printed directly onto the core. The production process is rather complicated and is only cost efficient in very large production volumes. Hydro printing inks are used to print the décor by a multicolour printing press with rollers that print directly onto the pre-sealed core.
Direct printing technology may be replaced with Digital Printing Technology that is much more flexible and small production volumes can be economically manufactured. The difference between these two methods is mainly the printing step where printing rollers are replaced by a digital non-contact printing process and where the desired image is directly applied on to the pre-finished core.
Digital printing may also be used to print on a paper sheet that is used in conventional laminate production and laminated under heat and pressure. The printing may be made prior to or after impregnation.
Paper and plastic foils are also used as surface layers in flooring and such materials may also be printed digitally.
Recently new “paper free” floor types have been developed with solid surfaces comprising a substantially homogenous powder mix of fibres, binders and wear resistant particles.
The powder mix may comprise aluminium oxide particles, melamine formaldehyde resins and wood fibres. In most applications decorative particles such as, for example, colour pigments are included in the mix. In general all these materials are applied in dry form as a mixed powder on a HDF core and cured under heat and pressure to a 0.1-1.0 mm solid layer. The powder is prior to pressing stabilized with moisture and UV lamps such that it forms an upper skin layer similar to a paper layer and this prevents the powder from blowing away during pressing. Melamine formaldehyde resin and wood fibres may be replaced by thermoplastic particles.
Several advantages over known technology and especially over conventional laminate floorings may be obtained such as increased wear and impact resistance, deep embossing, increased production flexibility and lower costs.
Powder technology is very suitable to produce a decorative surface layer, which is a copy of stone and ceramics. It is however more difficult to create designs such as, for example, wood decors. However, recently digital powder printing has been developed and it is possible to create very advanced designs of any type by injecting ink into the powder and create a digital print in the powder prior to pressing. The surface structure is made in the same way as for laminate flooring by a structured press plate, steal belt or an embossed matrix paper that is pressed against the powder.
Floors with a surface of wood are produced in many different ways. Traditional solid wood floors have developed into engineered floors with wood layers applied on a core made of wood lamellas, HDF or plywood. The majority of such floors are delivered as pre-finished floors with a wood surface that is coated with several transparent layers in the factory. Recently wood floorings have also been produced with a digitally printed pattern that improves the design of the wood grain structure in wood species that do not have a sufficient surface quality.
Digital printing is used in several floor types to create a décor. However the volumes are still very small mainly due to the high cost of the ink and the high investment cost for the industrial printers. It would be a major advantage if the ink cost could be reduced and if more cost efficient equipment could be used in an industrial scale.